Continuity mistake: Before taking Michael's mask, Corey calls Allyson and tells her to meet him at the diner at 9:00 pm. Later we see Allyson at the diner waiting for Corey, but when she checks her phone and sees Laurie is calling the time is 5:36 pm. (01:13:56 - 01:24:41)
Continuity mistake: In the beginning credits Lindsays name is spelled Lindsey. In the ending credits its spelled Lindsay, the correct way.
Continuity mistake: When Corey is almost hit by a car in the beginning (after the credits roll), his bike is suddenly toppled much further over after the camera cuts to a wideshot.
Answer: Michael's primary target is Laurie but, since he's also going around killing random people, most likely everybody believes that Michael is killing anybody who gets in his way to get to Laurie.